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cylsph_c

 Procedure Abstract Required_Reading Keywords Brief_I/O Detailed_Input Detailed_Output Parameters Exceptions Files Particulars Examples Restrictions Literature_References Author_and_Institution Version Index_Entries

Procedure

cylsph_c ( Cylindrical to spherical )

void cylsph_c ( SpiceDouble    r,
SpiceDouble    clon,
SpiceDouble    z,
SpiceDouble *  colat,
SpiceDouble *  slon )

Abstract

Convert from cylindrical to spherical coordinates.

None.

CONVERSION
COORDINATES

Brief_I/O

VARIABLE  I/O  DESCRIPTION
--------  ---  -------------------------------------------------
r          I   Distance of point from z axis.
clon       I   Angle (radians) of point from XZ plane.
z          I   Height of point above XY plane.
radius     O   Distance of point from origin.
colat      O   Polar angle (co-latitude in radians) of point.
slon       O   Azimuthal angle (longitude) of point (radians).

Detailed_Input

r           is the distance of the point of interest from z axis.

clon        is the cylindrical angle (radians) of the point from the
XZ plane.

z           is the height of the point above XY plane.

Detailed_Output

radius      is the distance of the point from origin.

colat       is the polar angle (co-latitude in radians) of the point.
The range of `colat' is [-pi, pi].

slon        is the azimuthal angle (longitude) of the point
(radians). `slon' is set equal to `clon'.

None.

Error free.

None.

Particulars

This returns the spherical coordinates of a point whose position
is input through cylindrical coordinates.

Examples

The numerical results shown for these examples may differ across
platforms. The results depend on the SPICE kernels used as
input, the compiler and supporting libraries, and the machine
specific arithmetic implementation.

1) Compute the cylindrical coordinates of the position of the
Moon as seen from the Earth, and convert them to spherical
and rectangular coordinates.

Use the meta-kernel shown below to load the required SPICE
kernels.

KPL/MK

File name: cylsph_ex1.tm

This meta-kernel is intended to support operation of SPICE
example programs. The kernels shown here should not be
assumed to contain adequate or correct versions of data
required by SPICE-based user applications.

In order for an application to use this meta-kernel, the
kernels referenced here must be present in the user's
current working directory.

The names and contents of the kernels referenced
by this meta-kernel are as follows:

File name                     Contents
---------                     --------
de421.bsp                     Planetary ephemeris
naif0012.tls                  Leapseconds

\begindata

'naif0012.tls'  )

\begintext

End of meta-kernel

Example code begins here.

/.
Program cylsph_ex1
./
#include <stdio.h>
#include "SpiceUsr.h"

int main( )
{

/.
Local variables
./
SpiceDouble          clon;
SpiceDouble          colat;
SpiceDouble          et;
SpiceDouble          lt;
SpiceDouble          pos    ;
SpiceDouble          r;
SpiceDouble          rectan ;
SpiceDouble          slon;
SpiceDouble          z;

/.
Load SPK and LSK kernels, use a meta kernel for
convenience.
./
furnsh_c ( "cylsph_ex1.tm" );

/.
Look up the geometric state of the Moon as seen from
the Earth at 2017 Mar 20, relative to the J2000
reference frame.
./
str2et_c ( "2017 Mar 20", &et );

spkpos_c ( "Moon", et, "J2000", "NONE", "Earth", pos, &lt );

/.
Convert the position vector `pos' to cylindrical
coordinates.
./
reccyl_c ( pos, &r, &clon, &z );

/.
Convert the cylindrical coordinates to spherical.
./
cylsph_c ( r, clon, z, &radius, &colat, &slon );

/.
Convert the spherical coordinates to rectangular.
./
sphrec_c ( radius, colat, slon, rectan );

printf( " \n" );
printf( "Original rectangular coordinates:\n" );
printf( " \n" );
printf( " X           (km):  %19.8f\n", pos );
printf( " Y           (km):  %19.8f\n", pos );
printf( " Z           (km):  %19.8f\n", pos );
printf( " \n" );
printf( "Cylindrical coordinates:\n" );
printf( " \n" );
printf( " Radius      (km):  %19.8f\n", r );
printf( " Longitude  (deg):  %19.8f\n", clon*dpr_c ( ) );
printf( " Z           (km):  %19.8f\n", z );
printf( " \n" );
printf( "Spherical coordinates:\n" );
printf( " \n" );
printf( " Colatitude (deg):  %19.8f\n", colat*dpr_c ( ) );
printf( " Longitude  (deg):  %19.8f\n", slon*dpr_c ( ) );
printf( " \n" );
printf( "Rectangular coordinates from sphrec_c:\n" );
printf( " \n" );
printf( " X           (km):  %19.8f\n", rectan );
printf( " Y           (km):  %19.8f\n", rectan );
printf( " Z           (km):  %19.8f\n", rectan );
printf( " \n" );

return ( 0 );
}

When this program was executed on a Mac/Intel/cc/64-bit
platform, the output was:

Original rectangular coordinates:

X           (km):      -55658.44323296
Y           (km):     -379226.32931475
Z           (km):     -126505.93063865

Cylindrical coordinates:

Longitude  (deg):         261.65040211
Z           (km):     -126505.93063865

Spherical coordinates:

Colatitude (deg):         108.26566077
Longitude  (deg):         261.65040211

Rectangular coordinates from sphrec_c:

X           (km):      -55658.44323296
Y           (km):     -379226.32931475
Z           (km):     -126505.93063865

2) Create a table showing a variety of cylindrical coordinates
and the corresponding spherical coordinates.

Corresponding spherical and cylindrical coordinates are
listed to three decimal places. All input and output angles
are in degrees.

Example code begins here.

/.
Program cylsph_ex2
./
#include <stdio.h>
#include "SpiceUsr.h"

int main( )
{

/.
Local parameters.
./
#define NREC         11

/.
Local variables.
./
SpiceDouble          colat;
SpiceDouble          rclon;
SpiceDouble          slon;

SpiceInt             i;

/.
Define the input cylindrical coordinates. Angles
in degrees.
./

SpiceDouble          r      [NREC] = { 0.0, 1.0, 1.0,
0.0, 1.0, 1.0,
0.0, 1.0, 1.0,
0.0, 0.0      };

SpiceDouble          clon   [NREC] = {   0.0,   0.0,  90.0,
0.0, 180.0, -90.0,
0.0,  45.0, 180.0,
180.0,  33.0        };

SpiceDouble          z      [NREC] = {  0.0,  0.0,  0.0,
1.0,  1.0,  0.0,
-1.0,  0.0, -1.0,
1.0,  0.0       };

/.
Print the banner.
./
printf( "    r       clon      z      radius   colat     slon \n" );
printf( " -------  -------  -------  -------  -------  -------\n" );

/.
Do the conversion. Output angles in degrees.
./
for ( i = 0; i < NREC; i++ )
{

rclon = clon[i] * rpd_c ( );

cylsph_c ( r[i], rclon, z[i], &radius, &colat, &slon );

printf( "%8.3f %8.3f %8.3f ", r[i], clon[i], z[i] );
printf( "%8.3f %8.3f %8.3f\n",
radius, colat * dpr_c ( ), slon  * dpr_c ( ) );

}

return ( 0 );
}

When this program was executed on a Mac/Intel/cc/64-bit
platform, the output was:

r       clon      z      radius   colat     slon
-------  -------  -------  -------  -------  -------
0.000    0.000    0.000    0.000    0.000    0.000
1.000    0.000    0.000    1.000   90.000    0.000
1.000   90.000    0.000    1.000   90.000   90.000
0.000    0.000    1.000    1.000    0.000    0.000
1.000  180.000    1.000    1.414   45.000  180.000
1.000  -90.000    0.000    1.000   90.000  -90.000
0.000    0.000   -1.000    1.000  180.000    0.000
1.000   45.000    0.000    1.000   90.000   45.000
1.000  180.000   -1.000    1.414  135.000  180.000
0.000  180.000    1.000    1.000    0.000  180.000
0.000   33.000    0.000    0.000    0.000   33.000

None.

None.

Author_and_Institution

J. Diaz del Rio     (ODC Space)
B.V. Semenov        (JPL)
W.L. Taber          (JPL)
E.D. Wright         (JPL)

Version

-CSPICE Version 1.1.0, 02-JUL-2021 (JDR)

Changed the argument names "lonc" and "lon" to "clon" and
"slon" for consistency with other routines.

Edited the header to comply with NAIF standard.

-CSPICE Version 1.0.2, 26-JUL-2016 (BVS)